Method of calibrating electric-current meters.



V. H. TODD.

METHOD OF CALIBRATING ELECTRIC CURRENT METERS.

APPLICATION FILED MAR. 4. 1914.

1,182,818. Patented May 9, 1916.

Emma/bo a Vz'aor /71 mm.

wirweooco yrc'ron H. TODD, or onanen, NEW Assmnon or one-HALF TO WILLIAM F.

a 1 i it MEHRING, or LALLENTOWN, PENNSYLVANIA.

1 METHOD OF CALIBRATING ELECTRIC-CURRENT METERS.

1 '0 all whom itmay Concern Be it known that I, VICTOR H. Tom), a

citizenfof the United States residing at Orange, in the county of Essex and State of a New Jersey, have invented new and useful Improvements in Methods of Calibrating Electric-Current Meters, of which the following is a specification;

a Thisinvention relates to iIl'lPIOVelllQIltS in methods of calibrating electric, current meters and has particular application to a method whereby direct current meters employ ng apermanent magnet and a movable coil under the influence of such magnet may be calibrated.

is my purpose to provide a method of calielectric current meters employing a permanent magnet and a movable c011 under the influence thereof, whereby the strength i ofthe permanentmagnet ofthemeter to be calibratedis lessened succeeding the con-' necting of the meter in the line, the strength of the magnet being influenced until the meter corresponds with a standard or calibrated meter connected in the line. I

With the above andother objects in view the invention consists in the various steps set forth in and falling within the scope of Scythe appended claims.

the accompanying drawing the figure isl a diagrammat ic view illustrating an apparatus whereby my methodmay be carried intopractice. i

My method is particularly adapted tor the purposeof calibrating direct current meters of that type employinga permanent magnet anda movable coil underltheinfluence of a such magnet and consists in connectmgthe 40,

meterto'be calibrated and, a standard meter in multiple with a source of current and then subjecting the permanent-magnet of the unknown meter to a counter-fiux produced byan alternating current until the unknown designates a direct current meter embodya ing,- among other features, a permanent umagnet 1 and a coil2 disposed between the poles of the magnet I and' under the in- Specification of Letters Patent.

Application filed March 4, 1914. Serial No. 822,501.

In carrying out the present invention it Patented May 9, 1916.

fluence of the field or flux set up by the latter. i

B designates a standard meter and the standard meter and meter to .be calibrated a re connected in multiple or parallel with an electriccircuit 3 connected up with the suit able source of current.

4 designates a coil of wire wrapped in such manner as to produce a magnetic flux adapted, when the coil is disposed in proximity to thepermanent magnet 1 'ofthe unknown meter, to act in opposition to the field set up'by such magnet thereby lessening the effect of the field of the magnet on the movable coil 2. This calibrating coil, as the coil may be termed, is connected in circuit with a suitable source of alternating current sothat thecoil may be energized.

In practice the meters A and B are connected in circuit as illustrated in the drawring and the circuit 3 closed. As usual, the

flux, springs, resistance, etc., of the meter to be calibrated are so proportioned that the hand or finger of the instrument indicates more amperage or voltage as the case may be than it should. The circuit of the calibrating coil is now closed and such coil moved slowly into proximity to the permanent magnet 1 of the meter to be calibrated. As the calibrater coil approaches the magnet l the field set up by the latter is gradually weakened and the hand or finger of the meter A drops back slowly to a position of the hand corresponding to that of the meter B. \Vhen the hand of the meter A reaches a propel-position the calibrating coil is removed and the face or dial of the meter A calibrated lll the usual well known manner.

From the foregoing description taken in connection with the accompanying drawing the manner of carrying out my improved method will be readily apparent to those skilled in the art to which the invention appertains.

I claim r 1. The method of calibrating electric current meters employing a permanent magnet and a movable coil under the influence of the magnet, which consists in connecting the meter to be calibrated and a standard meter in multiple with an electric circuit and then subjecting the permanent magnet of the meter to be calibrated to afield produced by an alternating current until the unknown meter corresponds with the standard instrument.

v 2. The method of calibrating electric current meters employing a permanent magnet 5 and a movable coil under the influence of the magnet, which consists in connecting the meter to becalibrated and a standard meter in multiple with an electric circuit and then carrying an alternating current coil produc- 10 mg a magnetic flux into proximity to the magnet of the unknown meter and moving the coil gradually toward the magnet until the unknown meter corresponds with the standard instrument. .a

i In testimony whereof I aflix my signature 15 in presence of two witnesses.

VICTOR H. TODD.

Witnesses:

\VILLIAM F. MEIIRING, EMILIE F. H. FITCH. 

